This was my biggest obstacle. I used Dvorak for 3-4 years in the early 90's. It was great, and I often miss it, but such were the pre-laptop (and pre thumb-drive) days, and I had to move around a lot of machines that I either was not allowed to or couldn't install a Dvorak driver. So I switched back, but my speed and accuracy was no worse on Dvorak; I was about 30% quicker if memory serves; accuracy was about the same, or at least within statistical noise.

The other irritant was editor commands. I'm an emacs guy and some just didn't translate well. And I was working on a *nix system, and "ls" was the "ol" keys. Third finger for both letters. Ack!